A method called the hot filling is conventionally known as a method of filling synthetic resin bottles, such as polyethylene terephthalate (PET) resin bottles, with juices, teas, and the like, which require sterilization. According to this method, the bottle is filled with the contents at a temperature of about 90 degrees C., then capped, sealed, and cooled. After the cooling, the inside of the bottle falls under a considerably depressurized condition.
What is called a heat-resistant bottle is used in those applications requiring the hot filling described above. Such a bottle is provided with vacuum absorbing panels around the body and has a so-called vacuum absorbing function, that is, the function of inconspicuously absorbing or easing up deformation of the bottle caused by volume reduction under reduced pressure, without giving an impression of distorted deformation. For example, Patent Document 1 describes an invention which relates to a round bottle having six vertically long vacuum absorbing panels formed in a dented shape and disposed around the body axisymmetrically on the central axis.
With bottle size or capacity becoming smaller from 500 ml to 200 ml with 350 ml and 300 ml in between, naturally the body has a smaller surface area. Then, it becomes difficult for the vacuum absorbing panels to secure the surface area required for a vacuum absorbing capacity. Thus, various proposals have been made in the past regarding the shapes of vacuum absorbing panels that can effectively perform the vacuum absorbing function. See, for example, Patent Document 1.    [Patent Document 1] Published patent application JP2003-63516